1. Field of the Invention
The present invention relates to a measured object mounting tool used for placing a model of a dental prosthesis when three-dimensional coordinates of a shape of the model of the dental prosthesis, which is a measured object, are measured by a three-dimensional measuring device. Further, the present invention relates to a production method of three-dimensional data of a dental prosthesis for cutting a block when cutting the dental prosthesis by an automatic cutting machine using the measured object mounting tool so as to have the same shape as the model of the dental prosthesis, which is the measured object.
2. Description of the Conventional Art
As a general production method of the dental prosthesis such as an inlay, a crown, a bridge or the like, the following methods have been widely known. One method comprises casting of a metallic material by a lost wax casting method, to thereby produce the dental prosthesis. Another method comprises building up a ceramics material on a refractory model, and baking it in a vacuum electric furnace, to thereby produce a dental prosthesis for the purpose of aesthetic appreciation, such as a ceramic inlay, an all ceramic crown or the like.
However, as for the work for producing a dental prosthesis by the conventional method such as the lost wax casting method, the baking by the vacuum electric furnace or the like, almost all processes are carried out by manual labor of a dental technician. Further, the process by the manual labor is remarkably fine and complicated. Thus, such the process takes remarkable time and effort, and the quality of the dental prosthesis, such as accurate or not, is influenced by the level of skill of a dental technician.
Then, as a method for producing a dental prosthesis having the stable quality in a short time in more quantity without depending on manual labor of a dental technician, a dental CAD/CAM system for producing a dental prosthesis has been developed in recent years. In this technique, the dental prosthesis is produced by the steps of producing the three-dimensional shape data of the dental prosthesis such as the inlay, the crown, the bridge or the like using a three-dimensional measuring device, a computer or the like, and cutting the block for cutting of the dental prosthesis by an automatic cutting machine on the basis of the obtained three-dimensional shape data of the dental prosthesis.
As such the three-dimensional measuring device in the dental CAD/CAM system, for example, a device comprising a holding base for a measured object, a rotating jig for the holding base, a changing jig for a holding base rotating shaft, a changing jig for a holding base position, and a laser measuring part, is used (for example, refer to Japanese Patent Application Laid Open No. 5-332731).
Such the device is effective when a model of a small type dental prosthesis applied to only one tooth, such as the inlay, the crown or the like is measured to thereby produce three-dimensional shape data of the dental prosthesis. However, the device has a structure where only the holding base of the measured object is rotated by the rotating jig, so that there is a problem that a large size measured object such as a model of a large-sized type dental prosthesis applied to a plurality of teeth, like a bridge, a gypsum model of a plurality of remaining teeth, or the like, cannot be measured.
Then, for example, the following three-dimensional devices capable of measuring a large size measured object such as a model of a large size dental prosthesis applied to a plurality of teeth, like a bridge, a gypsum model of a plurality of remaining teeth, or the like, to thereby produce the three-dimensional shape data, has been developed. One is a device comprising a body base, a rotary stage, an XY stage, a drive control means, a measured object holding means, an R stage, a first laser displacement gauge, a Z stage, and a second laser displacement gauge (for example, refer to Japanese Paten Application Laid Open No. 7-181022). In this device, the XY stage is movable in a specified horizontal direction X and a horizontal direction Y rectangular to the direction X independently from the rotation of the rotary stage, and has a fitting part for fitting with another member. The drive control means controls the drives of the rotary stage and the XY stage respectively. The measured object holding means has a part to be fitted with a fitting part of the XY stage, and a fitting part for fitting with the measured object. The R stage is movable in the diameter direction of the rotary stage. The first laser displacement gauge is provided at the under face of the R stage so as to have an optical axis parallel to a rotating shaft of the rotary stage. The Z stage is movable in the direction parallel to the rotating shaft. The second laser displacement gauge is provided at the side face of the Z stage so as to be rectangular to the rotating shaft. Further, another is a device comprising Xθ and Yθ stages, a first drive means, X and Y stages, a fixing tool, a second drive means, an optical probe, and a computer (for example, refer to Japanese Patent Application Laid Open No. 2002-257511). In this device, the Xθ and Yθ stages are rotatable in Xθ and Yθ directions. The first drive means finely drives these Xθ and Yθ stages respectively. The X and Y stages move in X and Y directions on the Xθ and Yθ stages. The fixing tool fixes the measured object having the spherical face on the X and Y stages. The second drive means finely drives the X and Y stages respectively. The optical probe measures the three-dimensional coordinate values of the face of the measured object. The computer controls the first drive means and the optical probe, and also makes arithmetic processing of signal.
Those devices can measure a large size measured object, such as a model of the large size dental prosthesis applied to a plurality of teeth, like abridge, the gypsum model of the plurality of remaining teeth, or the like, and make the three-dimensional shape data. However, the devices are complicated themselves, are difficult to be controlled, and involve high production cost. Especially, as for the former device, since it is provided with two laser displacement gauges, there is a problem that the maintenance and production costs are high.
Then, the three-dimensional measuring device capable of measuring both a small measured object, such as a model of the small type dental prosthesis applied to the one teeth, like an inlay or a crown, and a large measured object, such as a model of a large type dental prosthesis applied to a plurality of teeth, like a bridge, or a gypsum model of a plurality of remaining teeth, or the like, and reducing the production and maintenance costs by having one laser sensor for measuring the shape of the measured object, is developed. That device comprises a rotary table, a XY table, and a measuring part for measuring three-dimensional coordinates of a shape of a measured object. In this device, the rotary table has a rotating shaft, the axis of which is Z axis. The XY table is arranged on the rotary table, movable in an X axial direction and a Y axial direction, and has a placing table fixed on the upper part thereof for a measured object mounting tool being provided thereon. The measuring part measures the three-dimensional coordinates of the measured object shape mounted to the measured object mounting tool on the placing table by one laser sensor, which rotationally moves on one plane containing the Z axis around a desired point on the Z axis and moves in the Z axial direction.
As a method for measuring a model of a dental prosthesis such as an inlay, a crown, a bridge or the like to thereby produce three-dimensional shape data by such the device, for example, the following methods have been carried out. One method comprises, providing a model of a dental prosthesis on the placing table in the three-dimensional measuring device so as to direct its jawbone side, which is to be engaged with an abutment tooth, to the side direction, measuring it, and thereby making the three-dimensional shape data. The model of the dental prosthesis is formed with a wax, a synthetic resin or the like. (Hereinafter, this method is referred to as “a former production method of three-dimensional shape data”.) Another method comprises, providing a model of a dental prosthesis in the state of being engaged with a model of an abutment tooth or a model of a residual ridge on the placing table in the three-dimensional measuring device, measuring it, removing the model of the dental prosthesis, measuring parts where the model of the dental prosthesis has been contacted in the model of the abutment tooth or the model of the residual ridge, and thereby producing the three-dimensional shape data of the model of the dental prosthesis on the basis of the respective measured values. The model of the dental prosthesis is formed with a wax, a synthetic resin or the like. (Hereinafter, this method is referred to as “a latter production method of three-dimensional shape data”.)
The above respective production methods of the three-dimensional shape data can be sufficiently used, when making three-dimensional shape data of a dental prosthesis by measuring a model of the dental prosthesis such as an inlay, a crown, a bridge or the like, which does not need comparatively high measuring accuracy and processing accuracy, to thereby make the dental prosthesis by cutting a block for cutting of the dental prosthesis by an automatic cutting machine on the basis of the produced three-dimensional data of the dental prosthesis. However, when making a dental prosthesis for an implant applied for only one implant fixture, for example, which requires remarkably high measuring and processing accuracies, even both of above production methods of three-dimensional shape data have a problem that it is quite difficult to produce the dental prostheses having the necessary dimensional accuracy.
As the dental prosthesis for an implant applied to only one implant fixture, for example, there is a dental prosthesis in which an artificial tooth and an engaging portion are formed to have an integral shape, and provided and fixed at an intra-oral side part of the implant fixture embedded into the jawbone, directly or through the conventional abutment. In addition, there is an abutment or the like, in which a part contacted with gingiva and a part fixed with an artificial tooth are designed corresponding to the shapes of the gingiva and adjacent teeth of a patient, who is applied with the dental prosthesis, and in which an engaging portion for engaging with the implant fixture embedded into the jawbone is provided. In such the engaging portion projected toward the jawbone side of the dental prosthesis for an implant, a projected and/or recessed engaging part is formed to have a sectional shape other than that of rotating body (regular hexagon in general). Thus, when three-dimensional shape data of a model of a dental prosthesis for the implant is produced by the above described former production method of three-dimensional shape data, there is a problem that the engaging portion cannot be accurately measured, since laser light of a laser sensor of a measuring part can not reach to the inner part of the engaging portion, and the placing table or the XY tables becomes an obstacle when measuring a part on the placing table side of the engaging part. On the other hand, when three-dimensional shape data of a model of a dental prosthesis for an implant is produced by the above described latter production method of three-dimensional shape data, it is necessary to prepare a model of the dental prosthesis for the implant and a model of a implant fixture or an abutment engaged with this model of the dental prosthesis for the implant and measure the portion contacted with the engaging portion of the model of the dental prosthesis in the implant fixture or the abutment. Thus, there is a problem that the time and labour are necessary for preparing the model of the implant fixture or the abutment. Further, when the portion contacted with the engaging portion of the model of the dental prosthesis in the implant fixture or the abutment is measured, there is a problem that the engaging portion cannot be accurately measured, since laser light of the laser sensor of the measuring part can not reach to the inner part of the engaging portion, like the case of the former production method of three dimensional shape data.
Further, the engaging portion of the dental prosthesis for the implant has a polygonal shape having corner parts, for example, regular hexagon in general, so that there is a problem that it is difficult to accurately measure this engaging portion by a laser sensor of a general three-dimensional measuring device. Further, if the produced three-dimensional shape data of the engaging portion of the dental prosthesis is even slightly differed from the actual shape of the engaging portion of the model of the dental prosthesis, there may be a problem that the dental prosthesis cannot be engaged well with the implant fixture, or is loosened after fixing with the implant fixture when the dental prosthesis is fixed with the implant fixture, as the dental prosthesis is made by cutting a block for the dental prosthesis by the automatic cutting machine on the basis of the inaccurate three-dimensional data of the dental prosthesis.
Further, even when the former or latter production method of three-dimensional shape data can obtain accurate three-dimensional shape data of the model of the dental prosthesis, there is a problem that the dental prosthesis according to the produced three-dimensional shape data cannot be accurately produced when the engaging portion has the shape having the corner parts, since the automatic cutting machine, which makes a dental prosthesis on the basis of three-dimensional shape data of a model of a dental prosthesis, cuts the block by using a rotationally cutting tool in general.